These types of control arrangement are generally known. The usual position, velocity and electrical power controls of drives in particular have this structure and method of operation.
Control arrangements usually operate as depicted in FIG. 1 in accordance with the principle of a desired variable x* which is used for the control of a control path 2 being fed to the control 1. The corresponding actual value x of the control path 2 is detected by means of an encoder and likewise fed to the control 1. Based on the desired value x* and the actual value x—as a rule on the basis of the difference between desired value x* and actual value x—the control 1 determines a manipulated variable u for the control path 2 and regulates the control path 2 in this way to the required desired value x*.
In practice the control arrangement does not operate in the optimum way. In particular interference variables z often effect the control path 2, so that the actual value x does not correspond to the desired value x* despite ideal control. Furthermore in many cases the detection of actual values is (slightly) prone to errors, meaning that the actual value x delivered by the encoder 3 does not correspond exactly to the real actual value of the control path 2. The detection of such deviations of the actual value x supplied by the encoder 3 from the current actual value and the correction of these deviations is a first object of the present invention.
Nested control arrangements are often also used for drives. An example of such a control arrangement is shown in FIG. 2.
In accordance with FIG. 2 a control arrangement for a drive features a position control 4, a velocity control 6 subordinate to the position control 5 and a power control 7 subordinate to the velocity control 6. The velocity control 6 can alternately operate as a “true” velocity control or a rotational speed control. The output signal of the power control 7 acts via a power regulator 8 on the drive 4. The actual current I is detected by means of a current sensor 9 and fed to a node point 10 in which the difference between the desired current I* and the actual current I is formed. An actual position value p is detected by means of a position sensor 11 and fed to a further node point 12, in which the difference between desired position value p* and actual position value p is formed.
The output signal of the position control 5 corresponds to a desired velocity value v*. An actual velocity value v is subtracted in a third node point 13 from the desired velocity value v*. The actual velocity value v is generally determined in a differentiator 14 based on the actual position value p.
The control arrangement depicted in FIG. 2 is normally operated with a clock, meaning that it repeats the execution of its control algorithm with a working clock T of for example 125 μs (corresponds to a clock frequency of 8 kHz).
With nested control arrangements in particular (see FIG. 2 for example) it can occur that although the actual value p of the outer control circuit (i.e. the actual position value p according to the example) may be in error, the error does not however disturb the control of the outer control circuit.
However the error in the actual value p of the outer control circuit can cause an error in the desired value v* of the subordinate control circuit, which has a disruptive effect.
The detection of these types of errors and their correction is a further object of the present invention.
A control arrangement for a drive is known from DE 102 06 747 A1,
with the control arrangement featuring a control by which required values and actual values of the drive are processed during the operation of the control arrangement within the framework of a desired-actual control,
with the control arrangement featuring a determination device, by which a respective derived value is determined iteratively during operation of the control arrangement and the derived value is assigned to an evaluation device,
with the evaluation device, during operation of the control arrangement, assigning the respective derived variable to a position value of the drive and after accumulation of a sufficiently large number of derived variables, determining characteristic values of a systematic error contained in the actual values,
with the evaluation device during operation of the control arrangement, determining correction values depending on the determined characteristic values and applying the correction values to the actual values.
The derived variable is derived in DE 102 06 747 A1 on the basis of the respective actual position value and a further actual position value. A transmission is arranged between the two position sensors which detect the two actual position values.
A control arrangement for an electrical drive is known from DE 198 09 739 A1,
with the control arrangement featuring a control by which, during operation of the control arrangement, required values and actual values of the drive are processed within the framework of a required-actual control,
with the control arrangement featuring a determination device by which a respective derived variable is determined iteratively during the operation of the control arrangement and the derived variable is assigned to an evaluation device,
with the evaluation device, during operation of the control arrangement, assigning the derived variable to a position value of the drive in each case and after accumulation of a sufficiently large number of derived variables, determining characteristic values of a systematic error contained in the actual values,
with the evaluation device, during operation of the control arrangement, determining correction values depending on the characteristic values determined and applying the correction values to the actual values,
with the derived value determined by the determination device being the speed-related speed ripple.
A control arrangement for an electrical drive is known from DE 102 17 020 A1,
with the control arrangement featuring a control by which, during operation of the control arrangement, required values
and actual values of the drive are processed within the framework of a required-actual control,
with the control arrangement featuring a determination device, by which during operation of the control arrangement a respective derived value is determined iteratively and the derived variable is assigned to an evaluation device,
with the evaluation device, during operation of the control arrangement, assigning the derived value in each case to a position value of the drive and, after accumulation of a sufficiently large number of derived variables, determining characteristic values of a systematic error contained in the actual values,
with the evaluation device, during operation of the control arrangement, determining correction values depending on the determined characteristic values and applying the correction values to the actual values,
with the variable determined by the determination device depending on the difference between the actual value and the required value.